Method for obtaining patterns in a layer

ABSTRACT

The invention relates in particular to a method for producing subsequent patterns in an underlying layer (120), the method comprising at least one step of producing prior patterns in a carbon imprintable layer (110) on top of the underlying layer (120), the production of the prior patterns involving nanoimprinting of the imprintable layer (110) and leave in place a continuous layer formed by the imprintable layer (110) and covering the underlying layer (120), characterized in that it comprises the following step: at least one step of modifying the underlying layer (120) via ion implantation (421) in the underlying layer (120), the implantation (421) being carried out through the imprintable layer (110) comprising the subsequent patterns, the parameters of the implantation (421) being chosen in such a way as to form, in the underlying layer (120), implanted zones (122) and non-implanted zones, the non-implanted zones defining the subsequent patterns and having a geometry that is dependent on the prior patterns.

TECHNICAL FIELD OF THE INVENTION

The invention relates in general to the production of two-dimensional(2D) or three-dimensional (3D) structures that is to say the formationof structures that have a profile having at least two discrete levels ofheights or that have an analog profile with a continuous variation inthe tangents of the shape of the profile.

It has a particularly advantageous use in the field of nanoimprintlithography in which the reliefs are first reproduced in a temporarymaterial in order for it to be possible to then faithfully transferthese reliefs, via the temporary material, into a substrate or a thinfilm.

The invention has an advantageous use in the production of structures inwhich the patterns formed in the underlying layer are buried orencapsulated.

PRIOR ART

The techniques of transferring reliefs via imprinting, also callednanoimprinting, are part of a generic technology that groups together amultitude of very different approaches that nevertheless all share acommon point: the use of a stamp or mold that allows a 2D or 3D patternto be transferred onto a surface or into the thickness of a material.All these approaches using the same technology thus have in common thefact that close contact between the original substrate of theinformation (the mold) and the substrate receiving this information (thesubstrate) is made during this operation.

In all cases, the nanoimprint technologies differ from conventionallithography methods (conventional photolithography using masks, electronlithography, X-ray lithography or ultra-violet or UV lithography) by thefundamental mechanism that creates the patterns. For all the aboveconventional techniques, the patterns are created via physico-chemicalcontrast. If it has a positive tonality, the resin exposed to light orto radiation can be selectively developed. The opposite occurs if theresin has a negative tonality. For nanoimprinting, the contrast istopographical: it is the movement of matter and the flow of the resin inthe cavities of the mold that allow the production of specific patterns.

FIGS. 1a to 1c illustrate an imprinting operation during which a mold100 penetrates a layer of resin 110 on top of a substrate 120 in orderto form patterns in the resin 110.

Once the patterns have been imprinted in the resin 110, they can betransferred into the substrate 120 via etching. Then, the patternsformed in the substrate 120 can be encapsulated by depositing anencapsulation layer that covers the totality of the patterns. Thematerial of the encapsulation layer can be different from that of thepatterns formed in the substrate 120. In this case, the encapsulationlayer can be in contact with the patterns.

These patterns transferred into the substrate 120 are thus buried underan encapsulation layer.

The known solutions do not allow buried patterns having relativelycomplex shapes and dimensions that are precisely controlled to beobtained in a simple and reproducible manner.

FIG. 1b illustrates an ideal case in which the reliefs of the mold 100come in contact with the substrate 120 while eliminating all presence ofresin 110 between the top of the reliefs of the mold 110 and thesubstrate 120.

In practice, the implementation conditions are such that in the majorityof cases, a pressure 105 of less than 100 bar is applied onto the mold100 for a time of less than one hour and at a temperature that does notexceed 100° C. In these conditions, it is thus observed that with thematerials used as a resin that are typically monomers, oligomers orpolymers, the properties of the latter are such that they do not allowthe reliefs of the mold 100 to reach the substrate 120 resin 110interface during the pressing.

Consequently, as illustrated in FIG. 1c , a residual layer 131 of resinremains present between the surface of the substrate 120 and the reliefsof the mold 100. The thickness 130 of this residual layer 131 isdependent on the pressing conditions, but also on the geometry of themold 100 and the initial volume of resin 110 available.

The problem of knowing whether a predictive approach to the pressingmethod could be proposed, in particular whether it is possible topredict the residual thickness 130 if the geometry of the mold 100 andthe initial thickness 112 of the imprinted polymer are known, thusrapidly arose. This is illustrated by FIG. 2, in which the surface of amold is defined using a function p(x, y) that describes its profile 210.

Given that the material to be imprinted can flow over distancesidentical to that of the sample, it is then possible to establish asimple criterion for knowing whether the mold can be completely filledor not. FIG. 2 shows an arbitrary profile of a 3D structure to beimprinted with the initial thickness 112 of material to be shaped, whichis noted hereinafter as hi, with S being the surface of the substrateand of the mold and p(x, y) being the mathematical function describingthe profile 210 of the mold. The calculation of the ratio (f) betweenthe volume to be filled in the mold (Vm) and the volume ofincompressible matter available (Vi) allows three configurations to beidentified.

$f = {\frac{Vm}{Vi} = {\frac{\int{\int_{S}^{\;}{{p\left( {x,y} \right)}{dxdy}}}}{h,S}\left\{ \begin{matrix}{< 1} \\{= 1} \\{> 1}\end{matrix} \right.}}$

For a ratio f of less than 1, the total filling of the mold is possiblesince the matter is present in excess. In this case, the theoreticalresidual thickness (h_(r)) can be calculated and is therefore given bythe following relation:

$h_{r} = {h_{i} - \frac{\int{\int_{S}^{\;}{{p\left( {x,y} \right)}{dxdy}}}}{S}}$

A ratio equal to 1 implies that the volume of matter available is equalto the volume to be filled, thus implying a theoretical residualthickness equal to zero. Finally, for a ratio of less than 1, thecavities of the mold cannot be completely filled.

It should be noted that this relation involves neither the pressingconditions (temperature, pressure, imprinting time) nor the propertiesof the material (viscosity, surface energy) and that consequently, itcannot be considered for describing the dynamics of the process. It canonly reflect an ideal final state of the method. It also must beemphasized that this approach is highly simplified and is only slightlyapplicable as such due to the complexity of the fluid (resin)interaction with the structure (mold) during the pressing step. It canbe verified, however, for the imprinting of patterns having a constantdensity, present on surfaces greater than several square millimeters(mm2). As soon as there is a modification of the density of the patternsto be imprinted, even over a short distance, this approach is no longervalid, and mold deformations during the pressing must be taken intoconsideration. This makes the predictive approach almost impossible, orvery difficult, even with advanced digital tools.

The presence of the residual layer 131 of resin is therefore a problemspecific to the technique of nanoimprinting. The presence of a residuallayer and its thickness lead to two totally new problem sets for theimplementation of the nanoimprinting:

-   -   after pressing, there is the problem of needing to eliminated        this residual layer 131 of resin while preserving the shape and        the dimensions of the imprinted patterns in order to obtain a        mask of resin having the same characteristics as those that        would be obtained with standard lithography techniques;    -   another problem is that of ensuring the uniformity of its        thickness in order to be able to carry out the technological        steps that follow without difficulty.

The first point is not a technological barrier when the material shapedthen becomes a functional element of the component being manufactured.In the large majority of situations, however, the imprinted resin isonly used as a mask in order to then transfer the topographicalinformation to an underlying material using an etching method. In thesecases, it is then necessary to have an etching method that is asanisotropic as possible (in the direction Z of the reference frameillustrated in FIG. 2), that is to say, that has an etching rateparallel to the plane of the substrate (plane X, Y) as low as possibleor even, ideally, zero. In the opposite cases, any step of etching theresidual thickness leads to modifications in the horizontal dimensionsof the patterns imprinted and thus to a loss of information that isgenerally unacceptable during the corresponding lithography step asillustrated in FIGS. 3a to 3d described below. The development ofetching methods that are as anisotropic as possible between twomaterials is a very common constraint in the field of microtechnologyand nanotechnology. Their implementation can be very complicated forvery small dimensions, smaller than 30 nanometers (nm), and for 3Dprofiles.

FIGS. 3a to 3d illustrate the problems set forth above that result fromthe need to need to remove the residual layer 131 of resin 110 afterimprinting, via a method that must also be able to take into account thepotential non-uniformity of this layer. It is only after removal of theresidual layer 131 that the etching of the underlying substrate 120 canthen be undertaken. FIGS. 3a to 3d show the impact of the horizontal 310and vertical 320 etching rates on the preservation of the originaldimensions.

It should be noted here that the uniformity of the residual thickness130 is thus an important element for facilitating its removal andallowing the use of the resin mask as an etching mask. As previouslymentioned, this value depends in general on the geometry of the mold,including geometric parameters such as the sizes of the variouspatterns, their densities, the ruptures in the symmetry of the structureof the patterns. The value for the residual thickness also depends, asseen in FIGS. 1 and 2, on the initial thickness 112 to be imprinted, aswell as on the imprinting conditions: temperature, force applied,imprinting time. In FIG. 3a , the references 131′ are used to illustratezones in which the residual thickness is smaller than under otherpatterns 131″.

One object of the present invention is therefore to propose a solutionthat at least partly limits the difficulties described above and thatallows protected or encapsulated patterns, the dimensions of which areprecisely controlled, to be obtained in a reliable and simple manner.

The other objects, features and advantages of the present invention willbe clear after an examination of the following description and theaccompanying drawings. It is understood that other advantages could beincorporated.

SUMMARY OF THE INVENTION

To achieve this goal, one aspect of the present invention relates to amethod for producing subsequent patterns in an underlying layer, themethod comprising at least one step of producing prior patterns in animprintable layer on top of the underlying layer. The production of theprior patterns involves nanoimprinting of the imprintable layer andleaves in place, at the bottom of the patterns, a residual thickness ofimprintable layer. The imprintable layer thus forms a continuous layercovering the underlying layer. The method comprises at least thefollowing step:

-   at least one step of modifying the underlying layer via ion    implantation in the underlying layer, the implantation being carried    out through the imprintable layer comprising the prior patterns, the    parameters of the implantation being chosen in such a way as to    form, in the underlying layer, implanted zones and non-implanted    zones, the non-implanted zones defining the subsequent patterns and    having a geometry that is dependent on the prior patterns.

Advantageously, the implantation of ions is carried out in such a waythat the underlying layer, typically a substrate, has a continuousnon-modified zone located between the modified zones and a face of theunderlying layer through which the ions penetrate during theimplantation.

Thus, the invention allows buried patterns, the dimensions of which areparticularly precisely controlled, to be obtained in the underlyinglayer. The zones modified during the implantation can be preserved or,on the contrary, removed.

Thus, an underlying layer is obtained having properties, for exampleoptical modified because of the presence of this implantation of buriedpatterns.

Moreover, the buried patterns obtained are protected by the continuouszone that extends transversely from the upper face of the underlyinglayer and to the patterns.

This solution for encapsulating patterns is moreover faster toimplement, less complex and less costly than a solution in which anencapsulation layer is deposited on zones that are already implanted oralready etched.

Moreover, the invention allows possibly complex and very precisepatterns to be obtained in the underlying layer while eliminating thedisadvantages usually engendered by the residual layer.

With the known methods, the etching of this residual layer that isinevitably obtained at the end of the imprinting leads to undesiredmodifications that are difficult to predict in terms of the shape and/orthe dimensions of the final patterns.

The invention, by being based on a step of modifying the underlyinglayer through the imprintable layer, allows the imprinted patterns orpatterns that are dependent on the imprinted patters to be transferredinto this underlying layer without having to remove the residual layer.The patterns obtained are not therefore deformed by a step of removingthe residual layer.

In the context of the present invention, the adjective “underlying” inthe expression “underlying layer” is relative only to the orientationand the direction of the implantation of the ions. The underlying layeris positioned downstream of the imprintable layer with respect to thedirection of implantation of the ions. In the following drawings, whenthe orientation and the direction of implantation of the ions arevertical and downward, the underlying layer is positioned lower than theimprintable layer. If the implantation is directed vertically andupwards, the underlying layer, still positioned downstream of theimprintable layer with respect to the direction of implantation of theions, would then be positioned higher than the imprintable layer in thedrawings.

-   Optionally, the invention can further comprise at least any one of    the following features:    -   Advantageously, the step of producing prior patterns is carried        out in such a way that for each of the patterns, the residual        thickness of the imprintable layer is less than the minimum        implantation depth of the ions implanted during said        implantation, the minimum depth being taken in the implantation        direction and starting from the surface of the imprintable        layer. Typically, this minimum thickness corresponds to a        residual thickness left in place by the nanoimprinting step.

The minimum thickness of the imprintable layer corresponds to theresidual layer. By adjusting the thickness of the residual layer, it isthus ensured that the ions can be implanted without modifying a zone ofthe underlying layer that extends from the upper face of this layer.This non-modified zone is continuous in a plane parallel to the mainplane in which the underlying layer extends.

-   -   Advantageously, the continuous non-modified zone located between        the modified zones and a face of the underlying layer through        which the ions penetrate during the implantation has a thickness        greater than or equal to 10 nm, preferably greater than or equal        to 20 nm, preferably greater than or equal to 30 nm and        preferably greater than or equal to 40 nm.    -   According to one embodiment, the materials of the imprintable        layer and of the underlying layer, as well as the parameters of        the implantation, in particular the nature of the ions, are        chosen in such ways that the materials of the imprintable layer        and of the underlying layer have identical capacities of        penetration of the ions.

Thus, under equal implantation conditions, in particular for the sameenergy of the ions, the ions penetrate a layer made of the material ofthe imprintable layer and a layer made of the material of the underlyinglayer in the same way.

Thus, when these layers are stacked, the implantation from theimprintable layer allows the patterns of this layer to be reproduced inthe underlying layer. The implantation can be called “conformal” sincethe profile defined by the border between the implanted zones and thenon-implanted zones reproduces the profile defined by the patternsimprinted in the imprintable layer.

This implantation of ions thus allows a transfer of patterns from theimprintable layer to the underlying layer to be carried out, thepatterns transferred being formed by the modified material of theunderlying layer.

-   -   According to one alternative embodiment, the materials of the        imprintable layer and of the underlying layer, as well as the        parameters of the implantation, are chosen in such ways that the        materials of the imprintable layer and of the underlying layer        have different capacities of penetration of the ions. Thus, the        implantation from the imprintable layer allows patterns not        identical to those of the imprintable layer to be generated in        the underlying layer. Typically, the patterns of the underlying        layer are scaled copies of those of the imprintable layer.

In general, the implantation conditions, the thickness of the residuallayer and the thickness of the possible buffer layer are adjusted insuch a way that in the modified zones, the ions are implantedcontinuously starting from the surface of the layer to be etched.

Alternatively, the minimum depth of implantation can be greater than thethickness of the residual layer plus the thickness of the possiblebuffer layer. Thus, in the modified zones, the ions are not implantedcontinuously starting from the surface of the layer to be etched.

Another object of the present invention relates to a microelectronicdevice comprising a plurality of patterns created using one or the otherof the methods of the invention. Microelectronic device means any devicemade with means from microelectronics. In addition to the devices havinga purely electronic purpose, these devices include, in particular,micromechanical or electromechanical devices (MEMS, NEMS . . . ) andoptical or optoelectronic devices (MOEMS . . . ).

BRIEF DESCRIPTION OF THE DRAWINGS

The goals, objects, features and advantages of the invention will bebetter understood from the detailed description of an embodiment of thelatter that is illustrated by the following accompanying drawings inwhich:

FIG. 1, consisting of FIGS. 1a to 1c , describes the steps of ananoimprinting operation according to the prior art.

FIG. 2 shows the definition of a mold using a function that describesits profile.

FIG. 3, consisting of FIGS. 3a to 3d , illustrates the problems posed bythe removal of the residual layer of resin after an imprintingoperation.

FIG. 4, consisting of FIGS. 4a to 4c , illustrates a method according toan embodiment of the invention in which structures buried in a substrateare created.

FIG. 5, consisting of FIGS. 5a to 5d , illustrates an alternative to themethod of FIG. 4, in which a protective layer on the imprintable layeris used.

FIG. 6, consisting of FIGS. 6a to 6d , briefly describes the main stepsof a method according to an embodiment of the invention particularlywell suited for the etching of SiOCH.

FIG. 7, consisting of FIGS. 7a and 7b , illustrates, in FIG. 7a , astack comprising a buffer layer and illustrates, in FIG. 7b , the resultof the implantation when varying certain implantation parameters.

The drawings are given as examples and are not limiting to theinvention. They are schematic representations of a principle intended tofacilitate the understanding of the invention and are not necessarily onthe scale of the practical applications. In particular, the relativethicknesses of the various layers, films reliefs and patterns are notrepresentative of reality.

DETAILED DESCRIPTION OF THE INVENTION

Before undertaking a detailed review of embodiments of the invention,optional features are listed below that can optionally be used incombination or alternatively:

-   -   According to one embodiment, the parameters of the implantation        comprise in particular a direction of implantation. The        direction of implantation (direction Z in the reference frame        illustrated in FIG. 4a ) is perpendicular to the main plane in        which the underlying layer extends. This is typically the plane        X, Y of the reference frame illustrated in FIG. 4 a.    -   According to one embodiment, the parameters of implantation are        chosen in such a way that the subsequent patterns have a        geometry identical to that of the prior patterns.    -   According to one embodiment, the materials of the imprintable        layers and of the underlying layer, as well as the nature of the        ions, are chosen in such a way that the penetration of the ions        into one of the materials out of the material of the imprintable        layer and the material of the underlying layer is greater than        the penetration of the ions into the other of the materials out        of the material of the imprintable layer and the material of the        underlying layer.    -   According to one embodiment, the method comprises, after the        modification step, at least one step of removing the modified        zones (122) carried out selectively with respect to the        non-modified zones, in such a way as to leave in place the        non-modified zones.    -   Advantageously, the method according to any of the previous        claims, wherein the removal step comprises a step of etching the        modified zones (122) selectively with respect to the        non-modified zones, the etching step being etching via a wet        process or a dry process.    -   According to one embodiment, after the modification step, at        least a portion and preferably all of the modified zones and of        the non-modified zone are preserved.    -   According to one embodiment, said non-modified zone extends over        the entire surface of the layer to be etched. Alternatively, it        only extends over a portion of the upper face of the layer to be        etched. According to one embodiment, it extends vertically in        line with only some of the modified zones.    -   Advantageously, the implantation is carried out on the whole        plate.    -   Preferably, the implantation of ions is carried out in such a        way that the underlying layer has a continuous non-modified zone        located between the modified zones and a face of the underlying        layer through which the ions penetrate during the implantation.        Thus, the underlying layer has a non-modified thickness        separating the modified zones from the outside of the underlying        layer. This thickness thus allows the modified zones to be        encapsulated and protected. These modified zones thus form        buried structures. They can have particular electric, optical,        magnetic, thermal, mechanical properties in particular different        from that of the non-modified zones, regardless of whether the        modified zones are preserved or etched.    -   If the modified zones are preserved, at least one of their        optical, electric, magnetic, thermal or mechanical properties is        different from that of the patterns formed by a non-modified        zone.    -   If the modified zones are removed, the patterns formed by the        non-modified zones are thus surrounded, at least partially by a        vacuum or a gas. The gas can be ambient air. It can also be a        gas injected into the cavity formed by the removal of the        modified zones. Indeed, gas can be injected via the input that        was used for the etching of the modified zones. A plug is then        formed in order to plug the input in order to preserve the gases        in the structure. At least one of the optical, electric,        magnetic, thermal or mechanical properties of the patterns        formed by the non-modified zones is thus different than that of        the gas that surrounds these patterns.    -   According to one embodiment, said etching of the modified zones        forms at least one cavity. At least one gas is introduced into        said cavity. According to one embodiment, a plug is then formed        in order to plug an opening through which said at least one gas        was introduced into the cavity. The introduction of this gas        allows the optical, electric, mechanical parameters of the        structure to be adjusted. Moreover, the presence of the        continuous layer allows this gas to be confined reliably and in        a simple manner inside the structure.    -   Preferably, the implantation is carried out using an implanter        configured in such a way as to only implant ions starting from a        non-zero depth of the underlying layer. Thus, the implanter does        not implant the ions continuously starting from the surface of        the underlying layer through which the ions are implanted.    -   According to one embodiment, the method comprises, between the        step of producing the prior patterns and the implantation step,        a step of depositing a protective layer covering the prior        patterns. Advantageously, this layer protects the prior patterns        during the implantation. The latter thus preserve, during the        implantation, the shapes and dimensions conferred by the        imprinting.    -   Preferably, the protective layer is a layer of carbon deposited        via a plasma.    -   According to an alternative embodiment, the underlying layer is        directly in contact with the imprintable layer.

Advantageously, the implantation parameter, in particular the energyimparted on the ions, the time and the implantation dose are chosen insuch a way that the implanted zones can be etched selectively withrespect to the non-implanted zones. Preferably, these implantationparameters allow the matter to go from a crystalline state to anamorphous state.

Preferably, the implantation of species relates to all the elements thatcan be implanted in the material to be etched, without causing adislocation of its atomic structure such that it would lead to anatomization of the matter implanted, are capable of being suitable.

For example, the ions implanted are taken from hydrogen (H2), helium(He), argon (Ar) and nitrogen (N2). Just one or several of these speciescan be implanted.

According to one embodiment, the implantation is carried outanisotropically, in at least one implantation direction substantiallyperpendicular to the plane in which the layer to be etched or asubstrate on which the layer to be etched is placed extends. In thedrawings, the preferred direction of implantation is the direction Z.

In the context of the present invention, the methods known to a personskilled in the art and software (SRIM, TRIM, CTRIM . . . ) that allowsthe resulting implantation, and in particular the depth of implantation,to be simulated on the basis of the conditions of implantations can beused. Among the parameters of the implantation are the following: thenature of the species implanted, the material of the underlying layer,the material of the imprintable layer, optionally the material of thebuffer layer, dose, energy, time of exposure of the implanted layer tothe beam of ions.

-   -   According to one embodiment, the underlying layer is a layer or        a substrate, the material of which is taken from: silicon,        silicon germanium, germanium, quartz. According to one        embodiment, the underlying layer is a thin film or an active        layer formed out of one or more conductive materials.    -   The imprintable layer is formed out of one or more imprintable        materials. It is typically formed out of an imprintable resin.    -   According to one embodiment, the underlying layer is directly in        contact with the imprintable layer.    -   According to one embodiment, the underlying layer is a layer or        a substrate, the material of which is SiOCH.    -   According to one embodiment, during the implantation, there is a        buffer layer on top of the underlying layer made of SiOCH,        located between the imprintable layer and the underlying layer.        According to one embodiment, the method comprises a step of        removing the imprintable layer, and during the removal step, the        buffer layer is on top of the underlying layer made of SiOCH.        Thus, the buffer layer protects the SiOCH during the step of        removing the imprintable layer. Indeed, the SiOCH, especially        when it is porous, can be damaged during this step. This        embodiment thus allows a very good surface state to be        preserved.    -   According to one embodiment, the buffer layer is made of SixNy        or SixOy, preferably of Sin or SiO2. According to one        embodiment, during the implantation, the buffer layer has a        thickness greater than or equal to 10 nm and preferably greater        than or equal to 20 nm.    -   According to one embodiment, the underlying layer forms the        active layer of a photovoltaic cell.    -   According to one embodiment, the underlying layer is a substrate        made of sapphire and forms, together with the subsequent        patterns, a patterned sapphire substrate (PSS).    -   According to one embodiment, the invention relates to a method        for manufacturing a light-emitting diode (LED) comprising a        patterned sapphire substrate (PSS), wherein the patterned        sapphire substrate (PSS) is obtained by the method of the        previous paragraph.    -   According to one embodiment, the invention relates to a method        for manufacturing a plurality of photovoltaic cells, comprising        a substrate covered with patterns, wherein the patterns are        obtained by the method according to the invention.

It is specified that in the context of the present invention, the terms“on”, “is on top of”, “covers” and “underlying” and the equivalentsthereto do not necessarily mean “in contact with.” Thus, for example,the deposition of a first layer on a second layer does not necessarilymean that the two layers are directly in contact with each other, butthis means that the first layer at least partly covers the second layerwhile either being directly in contact with it or being separated fromit by at least one other layer or at least one other element.

In the context of the present invention, the thickness of a layer istaken in a direction perpendicular to the main faces of the substrate onwhich the various layers rest. In the drawings, the thickness is takenin the direction Z.

In the context of the present invention, a three-dimensional (3D)pattern means a pattern having, in a given layer, for example a resin ora substrate, an analog profile with a continuous variation of thetangents of the shape of the profile like in FIG. 11 or having at leasttwo levels of depth below the upper face of the layer when the patternis hollow or at least two levels of height above an upper face of thelayer when the pattern is protruding. A pattern called 2D patterndesignates the particular case of a pattern only having two levels ofheight or depth like in the example of FIG. 1.

An embodiment of the present invention will now be described.

In a first step 410, an operation of nanoimprinting is carried out in aconventional manner in an imprintable layer 110 using a mold. The moldhas reliefs with possibly complex shapes. The imprintable layer 110 istypically formed in a layer of imprintable resin.

Preferably before the imprinting, the imprintable layer 110 has beendeposited on an underlying layer 120 intended to be etched.

The underlying layer is typically a substrate 120 or a thin film. In therest of the description, for reasons of conciseness and clarity,“substrate 120” designates this underlying layer below the imprintablelayer 110 and in which the patterns of the resin will be transferred.This term is not in any way limiting to the nature and the function ofthis layer. The terms “substrate”, “layer to be etched” and “underlyinglayer” are thus equivalent.

During the imprinting operation, there is no attempt, like it is done inthe techniques of the prior art, to minimize the thickness 130 of theresidual layer 131. On the contrary, it is ensured that the latter has athickness that is as homogenous as possible over the entire surface inquestion.

In a second step 420, an implantation 421 of ions of gaseous elements iscarried out with the goal of obtaining a structural modification of thematerial forming the layer 120 to be etched starting from its surface.

The ions used are taken, for example, from: hydrogen (H), argon (Ar),nitrogen (N) and helium (He).

The implantation is carried out through the imprintable layer 110preformed by nanoimprinting. The implantation is thus carried out atvarious depths in the substrate 120, reproducing the patterns in reliefof the imprintable layer 110 and thus forming a zone 112 of modifiedmaterial.

Indeed, if the capacity of the ions to penetrate the material of theimprintable layer 110 and that of the substrate 120 is substantiallyidentical, the depth of penetration of the ions, measured in theimplantation direction and at each point of the face of the imprintablelayer 110 through which the ions penetrate, is uniform. Thus, the depthof penetration reproduces the patterns of the imprintable layer 110. Theimplantation is thus conformal in the sense that the profile formed bythe border between the implanted zones and the non-implanted zonesreproduces the profile of the patterns imprinted in the imprintablelayer.

Consequently, the zones in the substrate 120 under the areas in whichthe thickness of resin is the smallest are modified to a greater depththan the zones in which the thickness of imprintable resin is large.

According to another embodiment, the depths of penetration of the ionsin the imprintable layer and in the substrate are intended to bedifferent. The patterns reproduced in the substrate are not thereforeconformal with respect to those of the imprintable resin. The patternsimplanted in the underlying layer are then scaled copies of the initialshapes. Preferably, the depth of penetration for the substrate(underlying layer) will be smaller since usually, the density of thematerial of the substrate is greater than the density of the imprintablematerial, and thus the penetration of the ions is made more difficult.

The modification obtained by the implantation of ions involves, forexample, making a material that is initially crystalline amorphous. Thematerial made amorphous is typically crystalline silicon (Si) that isvery widely used in the microelectronics industry. The implantation isadjusted in order for the zones of the layer or substrate 120 under thezones in which the thickness of resin is the greatest to not bemodified.

In the following step 430, the imprintable layer 110 can then beremoved. The method of removal is adapted to the type of resin used. Itcan be “wet” etching that is to say that it is carried out in a suitableliquid solution that dissolves the resin without attacking theunderlying layers. “Dry” etching can also be used, using a plasma formedin a confined chamber. These techniques are well known and routinelyused in the microelectronics industry.

The last step of the method of the invention involves removing the zones122 made of material modified by the implantation of ions in the layer120. This removal step is solely optional. This removal step is carriedout selectively with respect to the non-modified zones of the substrate120. The implantation and etching conditions must thus be adjusted insuch a way that the etching be selective for the zones 122 modified byimplantation with respect to the non-modified zones that are not, oronly much less, removed by etching.

For example, the removal of these zones 122 is carried out via wetetching, typically using tetramethylammonium hydroxide (TMAH) orhydrofluoric acid (HF) in an oxygen atmosphere.

After these steps, the profile imprinted in the resin is transferred tothe underlying layer 120, typically a substrate or a functional thinfilm of a device being manufactured.

It should be noted here that the method of the invention does notrequire the removal of the residual layer 131 of resin with all thedisadvantages mentioned in the prior art. One criterion of quality forthis residual layer is its uniformity in terms of thickness (in theplane X, Y). It has been noted that this uniformity is even easier to beobtained since minimizing it is not sought. This uniformity of thicknessof the residual layer 131 and of the reliefs allow faithful reproductionof the imprinted patterns via ion implantation that is thus carried outidentically over the entire surface of a wafer, the base element fromwhich microelectronic devices are routinely produced.

The explanations that follow provide additional and optional details onthe steps of the method of the invention and proposes specific examplesof embodiments.

The substrate or the layer 120 to be etched are typically made ofsilicon. More generally, all crystalline substrates, including thosemade of quartz and of sapphire, can benefit from the implementation ofthe method of the invention. Those made of silicon also have theadvantage of being compatible with all the methods developed formicrotechnologies and nanotechnologies.

The material forming the layer 110 that is used as a temporary mask canbe, as seen above, a resin used in lithography or an inorganic polymerof the type obtained by “sol-gel” methods. As discussed in the priorart, the formation of the 3D patterns in the layer 110 conventionallyuses the technology of nanoimprint lithography using a mold that itselfcontains the patterns to reproduced. If the mold is manufactured from amaterial not transparent to the wavelengths of the ultraviolet (UV),which is the case for a mold made of silicon, for example, a thermalnanoimprint method and the use of a thermoplastic resin are involved.The thickness of resin deposited will be determined, as discussed in thechapter on the prior art, by the volume of the cavities of the mold thatmust be filled, while ensuring that the residual thickness afterpressing is not zero and at least equal to a minimum implantation depth.

In the case of the use of an implanter for this operation carried out instep 420, and as discussed below, the residual thickness isadvantageously at least greater than 30 nm which thus allows the speciesto be implanted up to the interface between the substrate 120 and theimprintable layer 110, the minimum implantation depth here being atleast 30 nm and more generally between 10 and 30 nm.

Moreover, as already mentioned, it is desired to optimize the imprintingmethod in such a way that the residual thickness be homogenous over theentire imprinted surface rather than seeking to minimize it as is thecase for the methods for transfer via dry etching. This phase ofoptimizing the homogeneity is generally reached when the residualthickness after pressing is more significant.

For the thermal imprint method, the latter can be created, for example,with a resin such as PMMA poly(methyl methacrylate), PS (polystyrene),at pressures from several bar to several tens of bars and at glasstransition temperatures of the resin (Tg) between +10° C. and +100° C.The step of removal from the mold, an operation in which the mold isseparated from the layer of resin, is carried out at temperatures lowerthan these transition temperatures (Tg) in such a way that the resin issolid at this time.

For the implantation step 420 an implanter called “beam line implanter”is conventionally used. This piece of equipment comprises a source forproducing ions, a particle accelerator using the electrostaticproperties of the ion in order to accelerate it, and a chamber for thetarget. The ions are thus accelerated and directed towards the targetwhere the device to be implanted is located. In this case, the depthimplanted can reach several tens of nanometers. However, it is difficultto implant on the surface because there is a non-zero minimum energyprovided to the ions that is 1 keV (kilo-electron volt). This minimumenergy inevitably causes penetration of the implanted ions into thesubstrate. The ions are therefore at a distance from the surface of thelatter, even if this is at a small depth. There is thus a zone betweenthe surface and this depth that does not have any or has a very smallconcentration of implanted species. This does not therefore allow asurface modification, of approximately only several nanometers, to becarried out.

The minimum implantation depth that can be obtained in these conditionsis approximately 30 nm.

However, in the context of the present invention, it is sought toimplant a zone that is buried. Thus, the ions are not implanted startingfrom the surface of the underlying layer 120. This allows the definitionof a zone, non-implanted from extending the surface of the underlyinglayer 120.

If the minimum implantation depth is greater than the thickness ofcertain zones of the imprintable layer, then the underlying layer is notmodified from its surface under these zones. More specifically, an upperarea of the underlying layer, extending from its surface, is notmodified.

The addition of a buffer layer 510, one advantage of which will bementioned below, must be controlled in order for the ions, onceimplanted, to only be implanted starting from a non-zero depth. Thus,the thickness of the residual layer 131 is chosen in such a way that itis less thick than the minimum depth of the implantation.

The thickness of this layer thus allows the substrate 120 to beimplanted while producing a non-implanted continuous layer 127 on thesurface of the layer 120 to be etched. In this type of reactor, theimplantation is carried out at a given depth, generally labeled Rp.Around this depth Rp, the implantation zone typically extends overseveral tens of nanometers in the implantation direction. In order toobtain a modification of the substrate that is continuous but buriedunder a non-implanted layer, it is therefore necessary to ensureoverlapping of the modified depths of the substrate after eachimplantation step.

An example of the results of an implantation operation carried out instep 420 is illustrated by FIG. 7b . This implantation is applied to thestack of layers illustrated in FIG. 5 a.

The stack successively comprises a substrate 120, a buffer layer 510 andan imprintable layer 110. In this example, the buffer layer 510 is madefrom SiARC, an anti-reflective material routinely used in lithography.In this case, it has a thickness of 100 nm for an implantation in thesilicon forming the substrate that extends 520 over a depth of 350 nm.

As can be seen in FIG. 7b , in this example, five successiveimplantations of hydrogen (H) ions with energies between 5 and 25 keVand the same dose of 10¹⁵ atoms/cm² are carried out. The conditions arecalculated in order for there to be overlapping of the implantationprofiles. The implantations are obtained at depths and with overlappingas indicated in table 530.

In this example, in order to obtain modified zones 122 located under anon-modified layer 127 extending from the upper face of the layer 120 tobe etched, it can be seen that the implantations at 5 and 10 keV must beavoided.

The step of removing the imprintable layer 110 is then carried out forexample in an etching chamber using chemistry based on oxygen or via awet process using chemistry routinely used by a person skilled in theart using a mixture called SPM of sulfuric acid (H2SO4) combined withhydrogen peroxide or oxygenated water (H2O2). This step is perfectlyknown and mastered by a person skilled in the art.

It should be noted that in order to access the modified zones 122 buriedunder the non-modified layer 127, it can be useful to make openings 123.The etching solution is introduced via these openings.

The conditions of removal of the modified layer must be such that thismethod must not consume any or consume only a little of the non-modifiedmaterial that is to say not more than several nanometers per minute.Typically, the substrate is made of silicon and the silicon madeamorphous by the implantation must be removed under the conditionsdescribed, selectively with respect to the crystalline silicon. Asalready mentioned, the use of tetramethylammonium hydroxide (TMAH) orhydrofluoric acid (HF) in an oxygen atmosphere is particularlyadvantageous. The crystalline silicon is indeed not at all or onlyslightly consumed by this type of cleaning.

The paragraphs below describe another advantage directly linked to theresidual thickness 131 that remains at the bottom of the patterns afternanoimprinting.

Indeed, this residue of resin, usually perceived as a disadvantage ofnanoimprinting, is used here as a protective layer that protects thelayer 120 to be etched during the implantation. This residual thickness131 is not etched, or not entirely etched, during the implantation step421. Vertically in line with the nanoimprinted patterns, the layer 120to be etched is thus not exposed during the implantation.

This embodiment provides a significant advantage. Indeed, in the absenceof a residue having a sufficient thickness, the desired implantation ofthe layer 120 to be etched inevitably produces a bombardment of thesurface of the carbon imprintable layer 110. This masking layer 110 isthus atomized on the surface. This bombardment tends to radiate atoms ofcarbon initially present in the imprintable layer 110. A portion ofthese atoms of carbon is projected into the layer 120 to be etched inthe locations where it is exposed. In the context of the development ofthe present invention, it was noted that these atoms of carbon penetratethe layer 120 to be etched and thus form, in this layer, a surface filmrich in carbon that can, according to the uses, modify the behavior ofthis layer. For example, this parasitic implantation of carbon canmodify the surface energy properties or the optical properties of thelayer 120 to be etched.

The invention, by providing a residual thickness 131 that prevents thelayer 120 to be etched from being exposed vertically in line with thenanoimprinted pattern of the imprintable layer 110, is able to protectthe face 128 of the layer 120 to be etched from any addition of carbon.The thickness 130 of the residual thickness 131 is chosen in such a waythat the atoms of carbon do not pass through it. Typically, thisthickness is greater than 20 nm and preferably greater than 30 nm duringthe implantation.

The residual thickness 131 covering the layer 120 to be etched isremoved, for example during the etching of the latter.

FIG. 4 that consists of FIGS. 4a to 4c , illustrates a particularembodiment of the present invention. This embodiment allows buried 3Dstructures to be created, the properties of which, for example electric,optical, magnetic, mechanical and thermal, are modified. Thisalternative comprises the following steps:

-   -   As illustrated by FIG. 4a , nanoimprinting of complex shapes in        an imprintable material 110 is carried out like in the step 410        previously described. As indicated above, preferably it is not        sought to minimize the thickness 130 of the residual layer 131        in order to ensure that the latter is homogenous over the entire        surface in question.    -   Then, as illustrated in FIG. 4b , an implantation of ions 421 is        carried out, for example hydrogen ions, through the imprintable        layer 110 preformed via nanoimprinting, to various depths, in        the underlying layer 120, that is to say, the substrate or the        thin film to be patterned. The zones in the underlying layer 120        under the areas in which the thickness of resin is the smallest        are modified to a greater depth. The material of the underlying        layer 120 is modified via implantation for example by making it        amorphous when it is initially crystalline. The zones of the        substrates under the zones in which the thickness of resin is        the greatest are not modified by the implantation. The        implantations are adjusted in this case in order for the zone        modified by the implantation closest to the interface with the        air that is to say the substrate/resin or layer/resin interface        to be buried under a predetermined thickness 126 in such a way        that it cannot be removed from the substrate or from the layer        by a dry or wet process. Thus, after the implantation, the        underlying layer 120 has a non-modified area 127 that is        continuous at the surface of the underlying layer 120 and        extends from the surface of this same layer 120 in the        implantation direction.

More specifically, the layer 120 to be etched has a non-modified zonebetween each zone 122 modified by implantation and the upper face 128 ofthis layer 120 to be etched. Thus, no zone 122 modified by implantationextends from the upper face 128 of this layer 120 to be etched. Theupper face 128 of this layer 120 to be etched is the face that is turnedtowards the layer that is imprintable and through which the ionspenetrate during the implantation 421.

This zone 127 is therefore continuous along the thickness of the stack,i.e. in the direction z of the reference frame illustrated in FIG. 4a .This non-modified zone 127 preferably extends over the entire surface ofthe layer 120 to be etched. Alternatively, it only extends over aportion of the upper face 128 of the layer 120 to be etched. Accordingto one embodiment, it extends vertically in line with only some of themodified zones 122.

The thickness 126 of the continuous non-modified zone 127 is notnecessarily constant over the entire surface of the layer 120 to beetched. In the example illustrated in FIG. 8b , this thickness isconstant.

Preferably, this thickness 126 is greater than or equal to 10 nm andpreferably greater than or equal to 20 nm, preferably greater than orequal to 30 nm and preferably greater than or equal to 40 nm.

Thus, the modified zones 122 are all located at a distance from theupper face 128 of the layer 120 to be etched.

This non-modified layer 127 allows the patterns formed by theimplantation 421 to be encapsulated.

In this embodiment, the minimum implantation depth is greater than thethickness of the residual layer 131.

-   -   As illustrated in FIG. 4c , the material 110 previously        nanoimprinted is then removed using dry and/or wet processes, as        already described, without affecting the modified zone that is        buried.

Thus, modified zones 122 are obtained that are encapsulated in thenon-modified material of the underlying layer 120.

According to one embodiment, the modified zones 122 are subsequentlyremoved selectively with respect to the non-modified material. For this,openings 123 are made in order to access these zones, as illustrated inFIG. 4 c.

In this case, the patterns formed by the non-modified zones are thussurrounded, at least partially, by a vacuum or gas. The gas can beambient air. It can also be a gas injected into the cavity formed by theremoval of the modified zones. Indeed, gas can be injected via the inputthat was used for the etching of the modified zones. At least one of theoptical, electric, magnetic, thermal or mechanical properties of thepatterns formed by the non-modified zones is thus different than that ofthe gas that surrounds these patterns.

If one or more gases are injected into the cavity or cavities, after theinjection, the openings 123 that were used for the etching of themodified zones and the injection of the gas must be closed. For example,a resin that plugs the openings 123 can be spin coated on. This resin ispreferably exposed to a source of light in order to stabilize it at thelocation of the opening 123, and the rest of the non-exposed resin isremoved by a treatment well known to a person skilled in the art. A plugis thus formed at the location of the openings 123.

According to another embodiment, the modified zones 122 are preserved.They are not removed selectively with respect to the non-modifiedmaterial. In this case, at least one of their optical, electric,magnetic, thermal or mechanical properties is different from that of thepatterns formed by a non-modified zone.

This solution for encapsulating and protecting patterns is particularlyadvantageous. Indeed, it is precise, allows very good size control ofthe patterns. Moreover, it is faster, less complex and less costly thata solution in which an encapsulation layer is deposited on thepreviously implanted zones or on the previously implanted and etchedzones.

-   FIG. 5 consisting of FIGS. 5a to 5e describes an alternative for the    implementation of the method in which, after the step, during which    the 3D patterns are formed in the imprintable layer 110, and before    the implantation step 421, an additional step is inserted during    which, as shown in FIG. 5b , a protective layer 115 covering the    prior patterns formed in the imprintable layer 110 and protecting    these patterns during the implantation 421 is deposited. This    protective layer 115 is advantageously a carbon layer 115. The    thickness deposited is several nanometers. Typically, 1 to 5    nanometers of carbon are deposited. This operation can be carried    out in a deposition or etching chamber in which a plasma is created    for example from methane (CH4). The carbon layer 115 may be    necessary for protecting the surface of the material imprinted via    nanoimprinting, advantageously resin, and thus limiting the    consumption of the latter during the implantation step 421 that    follows. If an etching chamber is used for this operation, a    capacitively (CCP) or inductively (ICP) coupled reactor, for    example, can be used. This type of deposition well known to a person    skilled in the art can be obtained in general by using gases such as    hydrocarbon (CxHy) or carbon fluoride (CxFy).-   The removal of the layer of carbon 115 can be carried out, for    example, via a plasma based on Oxygen.

As indicated above, the invention is particularly advantageous in thecase in which the underlying layer 120 is made of silicon or from one ofthe following materials: glass, silicon germanium, germanium, siliconnitride, sapphire, quartz.

According to yet another embodiment, the layer to be etched is made ofcarbon-doped hydrogenated silicon oxide (SiOCH). This can be porous ordense SiOCH. This material has the advantage of having a very lowpermittivity, in particular when it is porous.

All the embodiments described above can be applied to SiOCH. The mainsteps of a particularly advantageous embodiment will be described belowin reference to FIGS. 6a to 6 d.

1. 410—Stack and lithography (FIG. 6a ): A layer of resin forming theimprintable layer 110 is deposited on an underlying layer 120 of SiOCHthat can itself rest on a substrate 121, for example made of silicon.Between the imprintable layer 110 and the layer 120 of SiOCH, a bufferlayer 510 is formed, for example an oxide (SiO2) or more generally SixOyor a nitride (SiN) or more generally SixNy. This buffer layer 510 isused to facilitate the lithography as will be explained below. It alsoacts as a buffer layer for protecting the SiOCH during the implantation,since this material has a low density it is easily atomized.

Using this stack, a step of nanoimprint lithography (NIL) is carriedout. After pressing of the mold, a residue of resin 131 having athickness 130 remains at the bottom of the patterns. Moreover, as hasbeen described above, the residual thickness 131 forms a layer allowingthe atoms of carbon that are torn from the surface of the layer of resin110 and that have a tendency to penetrate the underlying layer 120 ofSiOCH to be stopped.

2. 420—Implantation (FIG. 6b ): The implantation 421 is carried outthrough the imprintable layer 110 and thus, vertically in line with thepatterns, through the residual thickness 131 and the buffer layer 510.The implantation 421 can be carried out in ion beam or plasma immersionion implantation equipment. The energy and the implantation dose aredefined according to the profile and the maximum depth desired for theimplantation and the minimum depth of the non-modified continuous zone127. The thickness of this zone 127 is labelled 126. Simulations on aCrystal TRansport of Ions in Mater (C-trim) applet allow the depth ofimplantation in the materials to be predicted.

The ion implantation leads to modifications in the material, inparticular the breaking of certain bonds. Under the effect of theimplantation, the SiOCH loses its methyl groups and tends to a structureclose or similar to that of an SiO2. This allows high selectivity duringthe wet etching to be created.

In the context of the present invention, it has been noted thatregardless of the species of the ion implanted, an atomization of theSiOCH takes place. The integration of the buffer layer 510 cited abovethus becomes particularly advantageous.

In the context of the development of the present invention, Hydrogenturned out to be particularly advantageous. Indeed, hydrogen allows veryhigh selectivity to be obtained when other species such as Argon show“infinite” resistance to wet etching with HF.

3. 430—Removal of the masking layer (FIG. 6c ): The removal of theimprintable layer 110 made of resin can be carried out via a wet or dryprocess. During this step, the buffer layer 510 advantageously protectsthe upper face 128 of the SiOCH. This face 128 is not therefore alteredby addition of carbon coming from the imprintable layer 110.

4. Etching of the modified SiOCH (FIG. 6d ) (optional step): Thisremoval step is optional. Indeed, it may be desired to preserve themodified SiOCH. If it is desired to remove it, the etching is preferablycarried out with a solution of HF diluted to 1%. As explained above, theimplantation generates modifications in the SiOCH that manifestthemselves as the hydrophilization of the material, the rupture of themethyl groups and finally the formation of the Si—O bonds. This providesinfinite selectivity with respect to the non-modified zone up to anetching time of less than 240 seconds.

This step also allows the buffer layer 510, for example made of SiN orSiO2, to be removed.

The technique described above for texturing SiOCH has severaladvantages:

-   -   The mask formed by the imprintable layer 110 is not metallic but        organic which confers numerous advantages in terms of method.    -   The nanoimprint lithography used to create the pattern is not        very costly and is accurate. Moreover, the resin residue at the        bottom of the pattern can act as a protective layer for        protecting the layer of SiOCH against the undesired addition of        carbon during the implantation as has been described above.        Moreover, it protects the SiOCH during the removal of the resin.    -   The etching is carried out via a wet process which allows size        control and a better surface state than with dry etching to be        preserved.

According to an alternative embodiment, the removal of the masking layer110 made of resin can be carried out during the step of wet etching withan HF solution, in particular if a resin containing Silicon such asHydrogen silsesquioxane (HSQ) is used.

The invention is not limited to the embodiments described above andextends to all the embodiments covered by the claims.

The invention claimed is:
 1. A method for producing subsequent patternsin an underlying layer, the method comprising at least one step ofproducing prior patterns in a imprintable layer on top of the underlyinglayer, wherein the production of the prior patterns comprisesnanoimprinting of the imprintable layer and leaves in place, at thebottom of the patterns, residual thicknesses of imprintable layer, theimprintable layer thus forming a continuous layer covering theunderlying layer, comprising the following step: modifying theunderlying layer via ion implantation in the underlying layer, theimplantation being carried out through the imprintable layer comprisingthe prior patterns and said residual thicknesses), the parameters of theimplantation comprise in particular an implantation direction andwherein the implantation direction is perpendicular to a main plan inwhich the underlying layer extends, the parameters of the implantationbeing chosen in such a way as to form, in the underlying layer, zonesmodified by the implantation and non-implanted zones, the non-implantedzones defining the subsequent patterns and having a geometry that isdependent on the prior patterns; wherein the step of producing priorpatterns is carried out in such a way that for each of the patterns, theresidual thickness of the imprintable layer is less than the minimumimplantation depth of the ions implanted during said implantation, theminimum depth being taken in the implantation direction and startingfrom the surface of the imprintable layer wherein the implantation ofions is carried out in such a way that the underlying layer has acontinuous non-modified zone located between the modified zones and aface of the underlying layer through which the ions penetrate during theimplantation, wherein the underlying layer is a single homogeneouslayer, and wherein the non-modified zone extends on all the surface ofthe underlying layer, so that the subsequent patterns are protected bythe non-modified zone, the non-modified zone and the subsequent patternsbeing made of the same material.
 2. The method according to claim 1,wherein the materials of the imprintable layer and of the underlyinglayer, as well as the parameters of the implantation, in particular thenature of the ions, are chosen in such ways that the materials of theimprintable layer and of the underlying layer have identical capacitiesof penetration of the ions.
 3. The method according to claim 2, whereinthe parameters of the implantation are chosen in such a way that thesubsequent patterns have a geometry identical to that of the priorpatterns.
 4. The method according to claim 1, wherein the continuousnon-modified zone located between the modified zones and a face of theunderlying layer through which the ions penetrate during theimplantation has a thickness greater than or equal to 10 nm.
 5. Themethod according to claim 1, wherein, after the modification step, atleast a portion of the modified zones and of the non-modified zone arepreserved.
 6. The method according to claim 5, wherein the modifiedzones have properties different from that of the non-modified zones, theproperties being chosen out of electric, magnetic, thermal properties.7. The method according to claim 6, wherein the modified zones haveoptical properties different from that of the non-modified zones.
 8. Themethod according to claim 5, wherein, the implantation is carried outusing an implanter configured in such a way as to only implant ionsstarting from a non-zero depth of the underlying layer.
 9. The methodaccording to claim 1, comprising, between the step of producing theprior patterns and the implantation step, a step of depositing aprotective layer covering the prior patterns.
 10. The method accordingto claim 9, wherein the protective layer is a layer of carbon depositedvia a plasma.
 11. The method according to claim 1, wherein the ions aretaken from the following ions: hydrogen (H2), helium (He), argon (Ar)and nitrogen (N2).
 12. The method according to claim 1, wherein theunderlying layer (120) is a layer or a substrate, the material of whichis taken from: silicon, silicon germanium, germanium, quartz.
 13. Themethod according to claim 1, wherein the underlying layer is a layer ora substrate, the material of which is SiOCH.
 14. The method according toclaim 13, comprising a step of removing the imprintable layer andwherein during the removal step, there is a buffer layer on top of theunderlying layer made of SiOCH, located between the imprintable layerand the underlying layer.
 15. The method according to claim 14, whereinthe buffer layer is made of SixNy or SixOy, preferably of SiN or SiO2.16. The method according to claim 14, wherein during the implantation,the buffer layer has a thickness greater than or equal to 10 nm.
 17. Amethod for producing subsequent patterns in an underlying layer, themethod comprising at least one step of producing prior patterns in aimprintable layer on top of the underlying layer, wherein the productionof the prior patterns comprises nanoimprinting of the imprintable layerand leaves in place, at the bottom of the patterns, residual thicknessesof imprintable layer, the imprintable layer thus forming a continuouslayer covering the underlying layer, comprising the following step:modifying the underlying layer via ion implantation in the underlyinglayer, the implantation being carried out through the imprintable layercomprising the prior patterns and said residual thicknesses), theparameters of the implantation comprise in particular an implantationdirection and wherein the implantation direction is perpendicular to amain plan in which the underlying layer extends, the parameters of theimplantation being chosen in such a way as to form, in the underlyinglayer, zones modified by the implantation and non-implanted zones, thenon-implanted zones defining the subsequent patterns and having ageometry that is dependent on the prior patterns; wherein the step ofproducing prior patterns is carried out in such a way that for each ofthe patterns, the residual thickness of the imprintable layer is lessthan the minimum implantation depth of the ions implanted during saidimplantation, the minimum depth being taken in the implantationdirection and starting from the surface of the imprintable layer whereinthe implantation of ions is carried out in such a way that theunderlying layer has a continuous non-modified zone located between themodified zones and a face of the underlying layer through which the ionspenetrate during the implantation; and after the modification step, atleast one step of removing the modified zones carried out selectivelywith respect to the non-modified zones, in such a way as to leave inplace the non-modified zones.
 18. The method according to claim 17,wherein the removal step comprises a step of etching the modified zonesselectively with respect to the non-modified zones, the etching stepbeing etching via a wet process or a dry process.
 19. The methodaccording to claim 18, wherein said etching of the modified zones formsat least one cavity, wherein as least one gas in introduced into saidcavity, and wherein a plug is then formed in order to plug an openingthough which said at least one gas was introduced into the cavity. 20.The method for producing subsequent patterns in an underlying layer, themethod comprising at least one step of producing prior patterns in aimprintable layer on top of the underlying layer, wherein the productionof the prior patterns comprises nanoimprinting of the imprintable layerand leaves in place, at the bottom of the patterns, residual thicknessesof imprintable layer, the imprintable layer thus forming a continuouslayer covering the underlying layer, comprising the following step:modifying the underlying layer via ion implantation in the underlyinglayer, the implantation being carried out through the imprintable layercomprising the prior patterns and said residual thicknesses), theparameters of the implantation comprise in particular an implantationdirection and wherein the implantation direction is perpendicular to amain plan in which the underlying layer extends, the parameters of theimplantation being chosen in such a way as to form, in the underlyinglayer, zones modified by the implantation and non-implanted zones, thenon-implanted zones defining the subsequent patterns and having ageometry that is dependent on the prior patterns; wherein the step ofproducing prior patterns is carried out in such a way, that for each ofthe patterns, the residual thickness of the imprintable layer is lessthan the minimum implantation depth of the ions implanted during saidimplantation, the minimum depth being taken in the implantationdirection and starting from the surface of the imprintable layer whereinthe implantation of ions is carried out in such a way that theunderlying layer has a continuous non-modified zone located between themodified zones and a face of the underlying layer through which the ionspenetrate during the implantation, and wherein the underlying layerforms the active layer of a photovoltaic cell.
 21. The method forproducing subsequent patterns in an underlying layer, the methodcomprising at least one step of producing prior patterns in aimprintable layer on top of the underlying layer, wherein the productionof the prior patterns comprises nanoimprinting of the imprintable layerand leaves in place, at the bottom of the patterns, residual thicknessesof imprintable layer, the imprintable layer thus forming a continuouslayer covering the underlying layer, comprising the following step:modifying the underlying layer via ion implantation in the underlyinglayer, the implantation being carried out through the imprintable layercomprising the prior patterns and said residual thicknesses), theparameters of the implantation comprise in particular an implantationdirection and wherein the implantation direction is perpendicular to amain plan in which the underlying layer extends, the parameters of theimplantation being chosen in such a way as to form, in the underlyinglayer, zones modified by the implantation and non-implanted zones, thenon-implanted zones defining the subsequent patterns and having ageometry that is dependent on the prior patterns; wherein the step ofproducing prior patterns is carried out in such a way that for each ofthe patterns, the residual thickness of the imprintable layer is lessthan the minimum implantation depth of the ions implanted during saidimplantation, the minimum depth being taken in the implantationdirection and starting from the surface of the imprintable layer whereinthe implantation of ions is carried out in such a way that theunderlying layer has a continuous non-modified zone located between themodified zones and a face of the underlying layer through which the ionspenetrate during the implantation, and wherein the underlying layer is asubstrate made of sapphire and forms, together with the subsequentpatterns, a patterned sapphire substrate (PSS).
 22. A method formanufacturing a light-emitting diode (LED) comprising a patternedsapphire substrate (PSS), wherein the patterned sapphire substrate (PSS)is obtained by the method for producing subsequent patterns in anunderlying layer, the method comprising at least one step of producingprior patterns in a imprintable layer on top of the underlying layer,wherein the production of the prior patterns comprises nanoimprinting ofthe imprintable layer and leaves in place, at the bottom of thepatterns, residual thicknesses of imprintable layer, the imprintablelayer thus forming a continuous layer covering the underlying layer,comprising the following step: modifying the underlying layer via ionimplantation in the underlying layer, the implantation being carried outthrough the imprintable layer comprising the prior patterns and saidresidual thicknesses), the parameters of the implantation comprise inparticular an implantation direction and wherein the implantationdirection is perpendicular to a main plan in which the underlying layerextends, the parameters of the implantation being chosen in such a wayas to form, in the underlying layer, zones modified by the implantationand non-implanted zones, the non-implanted zones defining the subsequentpatterns and having a geometry that is dependent on the prior patterns;wherein the step of producing prior patterns is carried out in such away that for each of the patterns, the residual thickness of theimprintable layer is less than the minimum implantation depth of theions implanted during said implantation, the minimum depth being takenin the implantation direction and starting from the surface of theimprintable layer wherein the implantation of ions is carried out insuch a way that the underlying layer has a continuous non-modified zonelocated between the modified zones and a face of the underlying layerthrough which the ions penetrate during the implantation, and whereinthe underlying layer is a substrate made of sapphire and forms, togetherwith the subsequent patterns, a patterned sapphire substrate (PSS).